In recent years, fuel cells have drawn attention as an eco-friendly clean energy source that has high power generation efficiency and produces little harmful gas.
A solid oxide fuel cell (hereinafter also referred to simply as an “SOFC”), which is a type of fuel cells, comprises a fuel cell unit and a separator, and the fuel cell unit comprises a solid oxide electrolyte layer, a gas-permeable cathode electrode (air electrode) and a gas-permeable anode electrode (fuel electrode).
The fuel cell generates power when a fuel gas such as hydrogen or hydrocarbon and an oxygen-containing gas are supplied respectively to the anode electrode and the cathode electrode while the solid electrolyte layer serves as a partition wall.
The separator is in contact with the fuel cell unit to collect charges of the fuel cell unit and to form a fuel gas channel or an oxygen-containing gas channel between the fuel cell unit and the separator.
The cathode electrode of the fuel cell unit is made of a metal oxide, and such metal oxides have higher electric resistance than metals.
Accordingly, when charges travel a long distance in the cathode electrode, the power generation efficiency is decreased. To avoid this, a current collection assisting layer is provided between the cathode electrode and the separator to form a conductive path so as to reduce the electric resistance.
JP2008-108656A or Patent Document 1 discloses a fuel cell that comprises a current collection assisting layer that is disposed between a cathode electrode and a separator and comprises a metal felt and a metal mesh.